There is within the industrial premises high dynamics for loading, unloading and moving both inputs and outputs, which generally are piled onto plastic pallets to be moved by lifts. Said operations are generally carried out at a great speed, with the consequence of frequent impact of the pallets with the probes of said lifts and eventually said goods fall down from different heights. Therefore, the damages in the pallets are not only frequent, but an everyday problem and even more, a great amount of the damages result in the discarding of the pallets, whereby the replacement rate of said pallets is generally high, which to a certain measure influences the costs of operation of industries.
Several attempts have been carried out in order to provide pallets more resistant to impacts so, a great amount of patents related to this type of pallets can be found protecting several forms of pallets or pallets, as well as the process of obtaining the same; for instance, the US patent application No. 2007/0028814 A1, to Swistak and Moore, discloses “a pallet having segments for multiple purposes, wherein a portion to be filled with injected foam is included, wherein there is at least an injected foam hole, selectively disposed at the lower surface, so-called an interior hollow portion, provides at least a foam injection hole to seal said hole so that at least one element is projected downstream from at least a foam injection hole.” The pallet disclosed in said document allows the assembly of said pallet one upon another without problems, and furthermore, allows the injection of foam within special zones located near the columns of said pallets. The invention disclosed in the Swistak document has the disadvantage of using thermosetting foamed materials, which does not provides for the recycling of said pallet in a whole, and, furthermore, the material thereof is of high cost.
On the other side, the US patent application No. 2006/0236903 to Moore describes a hollow thermoplastic member or pallet, that can be made from polypropylene (PP) or high-density polyethylene (HDPE), having spaces in some zones of the pallet, such as the columns thereof, that can be filled with thermosetting polymer foam, such as polyurethane, low-density polyurethane foam, ceramics, glass or an expandable mineral foam; said foam having also a fire-retardant the characteristic of which is additional in said plastic pallet. The disadvantage of the product described by Moore et al is that the production of this type of pallet, when using a thermosetting polymer foam is consequently more expensive and has a greater production time; also, as it is known, this type of plastics are hardly recyclable.
Moore describes also in U.S. Pat. No. 6,705,237 a pallet including an upper deck, a support material arranged within said upper deck; an upper structure member supporting said upper deck; a plurality of foot or column members arranged on said upper structure member; and a lower structure member arranged on said plurality of foot or column members. Said upper deck includes a first half and a second half, arranged in communication with a greater surface of the first half; said pallet having several variations and being foldable or includes reinforce members within the reach of the pallet disclosed in said document. Due to the characteristics described in said Moore patent document, the production of said pallet is considered highly expensive and with a high production time and, additionally, the type of material utilized is not considered as recyclable.
Swistak U.S. patent application No. 20070028814 discloses a platform of the type described by Moore, including additionally orifices for the injection of foam, selectively located at the lower surfaces of the platform columns. Plugs are employed to seal the foam filling holes as well as the vents. In an additional embodiment, said plugs project from the surface of the platform and are coupled to grooves in the deck of a second platform, so as to prevent the movement of the platforms piled up on one another.
The production methods of plastic pallets also cover a great variety of alternatives; for instance, U.S. Pat. No. 5,417,167 (Sadr, 1995) teaches a plastic platform formed from string pieces and hollow plastic boards of plastic material that can be any virgin plastic, recycled plastics or a mixture thereof; and are formed by blow molding. Said string pieces and boards are hollow but have their ends closed up so as to prevent the admission of dirty, liquids or insects. Various alternatives are disclosed for the coupling between the parts, including the screw securing as well as connections joining said plastic pieces to one another, and the use of components separately coupled to the board and the string pieces. A similar technique is disclosed in U.S. Pat. No. 6,976,437 (Fisch et al, 2005).
U.S. Pat. No. 6,938,558 (Peres, 2005) describes a blow-molded plastic platform constituted by two parts, including ribbons fastened on the string pieces due to the sliding and coupling of the trail type. Said upper and lower surfaces of the string piece are plain and improve the distribution of the load.
Alternatively, the plastic platforms can be formed from separated apart upper and lower docks that are connected and locked in a certain manner, for instance, by mechanic means. Said upper and lower docks, independently, have each characteristic connecting means to be coupled; this technique for the pallets having the disadvantage of the cost of said two separated apart molds. Additionally, the impact to the platform during the use, such as, for example, of a forklift, can cause the side movement of the upper and lower decks, one relating another, resulting in the separation of said docks. Moreover, said platforms can be vulnerable to applied forces along the connection line between said upper and lower decks; therefore, there is the need of a platform more resistant to the impact along the connecting line, capable of provide securer coupling characteristics so as to prevent the separation of said decks.
Consequently, there is a great need to increase the resistance of the pallets to the impact provoked during their use, as well as to prevent the disassembling of both parts, whereby a low cost production and a 100% recyclable product are obtained.
Some modifications to the basic design of a platform include the addition, for instance, of anti-slipping surfaces, as shown in U.S. Pat. No. 4,051,784 (Nishitani et al, 1977), that teaches a plastic platform having a surface provided of a member of an anti-slipping layer made of gum; or U.S. Pat. No. 6,006,677 (Apps et al., 1999), that provides a platform made of synthetic resin with a textured surface, formed by scratch-brushing the surface with a wire brush. Said documents fail in pretending to obtain an anti-slipping surface due to the fact that, on the one side, said Nishitani document shows a gum layer attached and, on the other side, said pallet with anti-slipping surface described by Apps is a surface that must be brushed in order to obtain a rough zone which, in both cases and in a general manner, this object is hardly attained; and furthermore, they are not products resisting the impacts to be supported by said pallets daily.